Gas diffusion layer for solid polymer electrolyte fuel cell

Abstract

A gas diffusion layer for a solid polymer electrolyte fuel cell having a solid polymer electrolyte and a catalyst layer disposed adjacent to the solid polymer electrolyte, where the gas diffusion layer includes a carbon fiber woven cloth having a surface and a coating of a fluororesin (such as polytetrafluoroethylene) containing carbon black on the surface, wherein the carbon fiber woven cloth is adapted to be disposed in the solid polymer electrolyte fuel cell such that the coating is adjacent to the catalyst layer in the solid polymer electrolyte fuel cell. Preferably, the coating penetrates no more than one-half the thickness of the carbon fiber woven cloth. Most preferably, the coating penetrates no more than one-third the thickness of the carbon fiber woven cloth. The carbon fiber woven cloth may be pre-treated with a water-repellent fluororesin (such as polytetrafluoroethylene), or with a mixture of a fluororesin and carbon black, to enhance water repellency. In another aspect, the invention provides a solid polymer electrolyte fuel cell including a solid polymer electrolyte having first and second surfaces, a catalyst layer disposed on each of the first and second surfaces, and the gas diffusion layer of this invention disposed adjacent to said catalyst layer disposed on each of the first and second surfaces.

We claim: 
     
       1. A gas diffusion layer for a solid polymer electrolyte fuel cell having a solid polymer electrolyte and a catalyst layer disposed adjacent to the solid polymer electrolyte, the gas diffusion layer comprising a carbon fiber woven cloth having a surface and a coating of a fluororesin containing carbon black on said surface. 
     
     
       2. A gas diffusion layer as defined in claim 1, wherein the carbon fiber woven cloth is pre-treated with a water-repellent fluororesin. 
     
     
       3. A gas diffusion layer as defined in claim 2, wherein said water-repellent fluororesin is polytetrafluoroethylene. 
     
     
       4. A gas diffusion layer as defined in claim 1, wherein the carbon fiber woven cloth is pre-treated with a mixture of a fluororesin and carbon black to enhance water repellency. 
     
     
       5. A gas diffusion layer as defined in claim 1, wherein said fluororesin is polytetrafluoroethylene. 
     
     
       6. A solid polymer electrolyte fuel cell comprising a solid polymer electrolyte having first and second surfaces, a catalyst layer disposed on each of said first and second surfaces, and a gas diffusion layer as defined in claim 1 disposed adjacent to said catalyst layer disposed on each of said first and second surfaces. 
     
     
       7. In a solid polymer electrolyte fuel cell comprising a solid polymer electrolyte having first and second surfaces and a catalyst layer disposed upon each of said first and second surfaces, the improvement comprising a gas diffusion layer as defined in claim 1 disposed adjacent to said catalyst layer disposed on each side of said first and second surfaces. 
     
     
       8. A method of diffusing gas in a solid polymer electrode and a catalyst layer disposed adjacent to the solid polymer electrolyte, said method comprising the steps of: (a) providing a carbon fiber woven cloth having a surface;   (b) forming a coating of a fluororesin containing carbon black on said surface; and   (c) disposing said carbon fiber woven cloth in the solid polymer electrolyte fuel cell such that said coating is adjacent to said catalyst layer and such that gas diffuses in a surface direction along said carbon fiber media.